Organic solvents, such as hydrocarbons, halogenated hydrocarbons, glycol ethers, esters or ketones, are used in several applications, such as dry-cleaning of textiles or degreasing of metals. However, it is well known that halogenated hydrocarbons, glycol ethers, esters or ketones tend to decompose when they are exposed to heat, oxygen, light or water, particularly if metals or metal salts are present. Acidic products, such as hydrochloric acid, are produced during decomposition of halogenated hydrocarbons. Therefore, it is common in the industry to add a stabilizer to halogenated hydrocarbons.
The published Patent Application WO 0236531 discloses a stabilizer composition comprising an olefinic amine with a boiling point of 5 to 80° C., an aliphatic, acyclic ester or formate of 2 to 6 carbon atoms, optionally a saturated aliphatic amine with a boiling point of 5 to 80° C. and optionally an antioxidant, such as a cyclic alkane or a pentene.
U.S. Pat. No. 3,424,805 suggests stabilization of chlorinated hydrocarbons by addition of an aliphatic diamine, triamine or polyamine. It is taught that the stabilizing effect can be increased by the addition of an aliphatic monoamine, such as diisopropylamine or pyrrole or N-alkyl pyrrole, such as N-methyl pyrrole.
European Patent No. 1 042 257 discloses a stabilizer composition for halogenated hydrocarbons which comprises an N-alkyl morpholine and a straight-chain or cyclic aliphatic amine containing no heteroatoms other than nitrogen with a boiling point of at least 150° C.
European Patent No. 0 059 251 discloses a composition for stabilizing trichloroethylene. The composition comprises an amine with a boiling point of 50 to 150° C., ethyl acetate, N-methylpyrrol and/or an alkylphenol and further diisobutylene and/or cycloheptatriene and an ether comprising no hydroxyl groups.
Typically stabilizer compositions are not added to hydrocarbons due to their well-known stability against decomposition. However it has been observed that the lack of a stabilizer often leads to an undesirable concentration of acidic compounds in the hydrocarbon which originates from the decomposition of contaminants present in the dry-cleaning of textiles or degreasing of metals and which increases over time as the hydrocarbon is recycled. The same observation has been made when using glycol ethers, esters or ketones as a solvent. The produced acidic compounds can cause corrosion problems in the cleaning operations.
Unfortunately, the stabilizer compositions suggested in the prior art often do not meet the requirements of the industry for many applications. Often the capacity of the stabilizer is reduced over time too fast which is made apparent by an increase in acidity of the organic solvent. Many stabilizers suffer in that they are not suitable for solvents of low polarity, such as hydrocarbons. Yet other stabilizers have a very high boiling point and do not stabilize the solvent when it is in the vapor phase.
Accordingly, one object of the present invention is to provide a new stabilizer composition for organic solvents. A preferred object of the present invention is to provide a stabilizer or stabilizer composition which is suitable for stabilizing an organic solvent against an undue increase in acidity over an extended period of time. Yet another preferred object of the present invention is to provide a stabilizer or stabilizer composition which is sufficiently volatile to stabilize organic solvents in the vapor phase. Yet another preferred object of the present invention is to provide a stabilizer or stabilizer composition which can not only be used in halogenated hydrocarbons but also in solvents of medium or low polarity, such as glycol ethers, esters, ketones or hydrocarbons.